1. Field of the Invention
The present invention relates to eyeglasses, and particularly to a spring hinge using clutch structure for eyeglasses.
2. Description of the Related Art
As is known to all, spring hinge for eyeglasses has been used for many years. For example, a resilient hinge for spectacle frame is disclosed in Chinese patent No. 96194866.3. The resilient hinge can be directly connected to the lug or the side arm. It, with a rational structure, is durable and easy to control. The resilient hinge includes a male frame knuckle and a male side-arm knuckle rotatably interconnected by a pin. The contact surface of one of the knuckles has a diametrically extending projection with sloping sides for engaging a cross-shaped recess in the other knuckle. The recess defines the open and closed positions of the side arm. The disadvantages of such design are unsymmetrical, absonant and inaesthetic.
Also, a hinge equipment of the glasses frame is disclosed in Japanese patent application No. 10-152039. It relates to a hinge equipment of the glasses frame which helps the temples complete the motions of opening and closing by a cam mechanism. Each of the hinge knuckles of the ends of lens rim and the temples has a friction surface respectively. The friction surfaces which are rotatable with the hinge have a periodic function wave-like profile and are inconvenient to insert and remove. The portion of said frame engaging both of the temples and lens rim has a fixed element. The hinge knuckle of the fixed element, which retains a changeless relatively position of the hinge axis under an elastic force, has a same friction surface profile with the hinge knuckle of the end of the temples. The friction surfaces of said hinge knuckles occlude or converge in opposite directions under an elastic force to keep contacting and work cooperatively to complete the periodic intermittent hinge motion. The cam mechanism positions the temples when the temples rotate to open or close. The cam mechanism using the recess and the flange or the quadrate hole and quadrate axis to transmit force. Relative motion, concurring with the rotation motion, often needs a clearance fit which will result in a vacant position when the hinge rotates reversely. But avoiding the vacant position is very important especially for a hinge.